Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.93	13.480%	$196.241	$196.24	$196.25	$196.20
Purchase #2	$143.56	10.416%	$158.5132	$158.51	$158.50	$158.50
Purchase #3	$33.47	4.703%	$35.0441	$35.04	$35.05	$35.00
Purchase #4	$79.75	4.741%	$83.5309	$83.53	$83.55	$83.50
Purchase #5	$132.41	10.690%	$146.5646	$146.56	$146.55	$146.60
Purchase #6	$97.40	3.739%	$101.0418	$101.04	$101.05	$101.00
Purchase #7	$12.78	6.182%	$13.5701	$13.57	$13.55	$13.60
7 purchase totals =	$672.30		$734.5057	$734.49	$734.50	$734.40